Variable speed drive mechanisms have been devised which customarily employ a plurality of balls suspended within a special cage and interpositioned between rotatable drive and driven members so as to be capable of imparting rotation of the drive member to the driven member as determined by a sphere whose axis of rotation is dictated by pivotal follower elements or rollers. Representative of this approach are disclosed in U.S. Pat. Nos. Re. 29,631 to L. A. Schott; U.S. Pat. No. 312,171 to H. S. H. Shaw; U.S. Pat. No. 3,154,957 to M. Kashihara; and U.S. Pat. No. 4,011,765 to H. Tippmann. Of these patents, Kashihara is of interest for disclosing a single ball drive for transmission of relatively large torques by employing a dish-shaped drive wheel and driven wheel on diametrically opposed surfaces of a spherical member, the axis of rotation of the spherical member being controlled by a ball bearing assembly. Other patents of general interest in the field are U.S. Pat. Nos. 2,512,717 to R. H. Dicke; U.S. Pat. No. 2,682,776 to P. S. Morgan; U.S. Pat. No. 2,727,396 to Haugwitz; U.S. Pat. No. 3,039,328 to H. W. Christenson; U.S. Pat. No. 3,237,468 to H. Schottler; U.S. Pat. No. 3,216,283 to N. T. General; U.S. Pat. No. 3,267,755 to W. H. Isely; U.S. Pat. No. 3,269,190 to G. M. Laman; U.S. Pat. No. 3,272,025 to 0. Stieber; U.S. Pat. No. 3,395,589 to M. Gersten; U.S. Pat. No. 3,398,592 to J. Brany; U.S. Pat. No. 3,513,714 to M. D. Jennings et al; U.S. Pat. No. 3,826,157 to C. C. Stoll; U.S. Pat. No. 3,987,685 to W. J. Opocensky; and U.S. Pat. No. 4,024,771 to B. C. Joseph.
Although it has been proposed previously to employ fixed ratio drives of the frictional ball and roller type in automotive applications so as to maintain the speed of rotation of the engine constant as the resistant torque applied to the wheels is varied, it has been impractical to accomplish the same through the provision of a single ball and single pair of rollers, as alluded to in the aforementioned patent to Haugwitz; and particularly in the transmission of appreciable torque. Haugwitz concluded that a single ball with one pair of control rollers associated with it would be incapable of the necessary control over variations in speed, particularly in high torque applications, such as, automotive transmissions. As a result, in Haugwitz and subsequent developments of variable speed drive mechanisms, the approach has been to design the variable speed transmission with two or more balls each having its own gimbal and control roller members arranged in surrounding relation to the drive and driven members. This has necessitated rather elaborate design considerations particularly in the mounting and disposition of the balls so as to be freely journaled in a cage while making the cage itself pivotal in determining the speed ratio between the input and output side of the transmission. In addition to the aforementioned patents, another patent representative of the multi-ball approach in a variable speed drive is that to Floyd U.S. Pat. No. 3,071,018.
Accordingly, among the deterrents to single ball drives has been the inability to balance the forces applied to different points on the surface of the ball while having a ball large enough to transmit substantial horsepower. An associated deterrent has been to design a bearing structure for the input and output sides of the transmission which will adequately support the asymmetrical forces attendant to the operation of a single ball; and, equally as critical, to devise a control roller assembly which will establish the necessary degree of osculation so as to be capable of closely controlling the axis of rotation of the ball with respect to the drive and driven elements and make the transmission highly sensitive to desired changes in speed and torque. Nonetheless, utilization of a single ball drive offers a number of offsetting advantages if the aforementioned difficulties can be satisfactorily overcome. For instance, the single ball drive creates a synergistic effect in that a single ball of a given diameter is capable of transmitting considerably more horsepower than are two balls, each of which is one-half the diameter of the single ball; further a single ball will avoid unnecessary multiplication of parts and control elements, substantially reduce the overall size of the transmission and indeed result in higher efficiency, vastly reduced weight and minimize the degree of control required over the operation of the entire system. These advantages are of particular importance in automotive applications where size and weight considerations previously encountered in the application of frictional ball and roller technology to variable speed drives have effectively eliminated them from consideration. Here, reference is made to my copending application Ser. No. 207,190, filed Nov. 10, 1980 for ELECTRIC MOTOR DRIVE WITH INFINITELY VARIABLE SPEED TRANSMISSION, now U.S. Pat. No. 4,391,156 assigned to the assignee of the present invention, and incorporated by reference herein. As disclosed in said copending application for patent, a DC motor drive is coupled to a variable speed transmission through a flyball governor system, the latter operating a movable control member which is shiftable or pivotal to vary the speed ratio between the input and output sides of the transmission over a predetermined range. A predetermined resistance is imposed on the movement of the flyball governor so that the acceleration of the output side of the transmission is controlled independently of that of the motor drive with the maximum speed obtainable being matched to the most efficient operating speed level of the motor. Thus, the speed ratio of the transmission is established so that at lower vehicle speed ranges, the load requirements on the motor are minimized by being set at a predetermined ratio; and as the motor is accelerated the speed ratio will be gradually reduced to a ratio which will permit the motor to be operated at its most efficient performance level while delivering maximum power through the transmission. The present invention may be exemplified by its use in combination with such a motor drive as well as internal combustion engines and specifically in such a way as to be capable of delivering maximum horsepower through a single ball while greatly reducing the weight and size of the transmission, improving its wear and performance characteristics and enabling close sensitive control over the speed ratio between its input and output sides.